We performed a study to investigate whether some physiological processes are caused by electrical current when passing through the tissues and organs. The basic idea of diathermia, medical treatment and therapy with alternating high frequency electric current, is to use the transformation of electric power into heat when the current goes through the tissue and internal biological environment. The important fact in this process is to avoid the massive displacement of ions, which could be potentially destructing side effect. Advantage and importance of using the alternate current (with frequency ~1 MHz) over the direct current is explained, as well as the fact that this effect was spotted almost simultaneously by Nikola Tesla and Jaques d’Arsonval, at the end of 19th century. This paper also explains later the cooperation between two scientists and the basic principles of diathermy – heating effect with high frequency alternate current.